Microstructure

ABSTRACT

Disclosed is a microfine structure which can be used as an anisotropic conductive member. Also disclosed is a method for producing such a microfine structure. Specifically disclosed is a microfine structure which is composed of a base having penetrating micropores at a density of not less than 10,000,000 micropores/mm 2 . In this microfine structure, some penetrating micropores are filled with a substance other than the material of the base.

TECHNICAL FIELD

The present invention relates to a microstructure and its manufacturingmethod.

BACKGROUND ART

An anisotropic conductive member, when inserted between an electroniccomponent such as a semiconductor device and a circuit board, thensubjected to merely the application of pressure, is able to provide anelectrical connection between the electronic component and the circuitboard. Accordingly, such members are widely used, for example, asinspection connectors when carrying out functional inspections ofsemiconductor devices and other electronic components. The anisotropicconductive member can be expected to be applied to anisotropicconductive connecting members in various devices, and connecting membersfor optical transmission using light transmissive materials for thesubstrate of the anisotropic conductive member by controlling theconnecting portion as desired, and also to new graphic devices bycontrolling the filler arrangement.

Inspection connectors are used to avoid the large monetary losses thatare incurred when, upon carrying out functional inspections after anelectronic component such as a semiconductor device has been mounted ona circuit board, the electronic component is found to be defective andthe circuit board is discarded together with the electronic component.

That is, by bringing electronic components such as semiconductor devicesinto electrical contact with a circuit board through an anisotropicconductive member at positions similar to those to be used duringmounting and carrying out functional inspections, it is possible toperform the functional inspections without mounting the electroniccomponents on the circuit board, thus enabling the above problem to beavoided.

Such an anisotropic conductive member is described in JP 2000-012619 A,which discloses “an anisotropic conductive film comprising a filmsubstrate composed of an adhesive insulating material and a plurality ofconductive paths composed of an electrically conductive material whichare arrayed within the film substrate in a mutually insulated state andpass entirely through the film substrate in a thickness directionthereof, wherein the conductive paths have shapes, in a cross-sectionparallel to a lengthwise direction of the film substrate, withcircumferences having thereon an average maximum length between twopoints of from 10 to 30 μm, and wherein neighboring conductive pathshave intervals therebetween which are from 0.5 to 3 times the averagemaximum length.”

JP 2005-085634 A discloses “an anisotropic conductive film comprising afilm base composed of an insulating resin and a plurality of conductivepaths which are mutually insulated, pass entirely through the film basein a thickness direction thereof and are positioned in staggered rows,wherein conductive paths in mutually neighboring conductive path rowshave a smaller distance therebetween than conductive paths within asingle row of conductive paths.”

JP 2000-012619 A and JP 2005-085634 A disclose methods of manufacturingsuch anisotropic conductive films in which fine wires of an anisotropicconductive material are inserted into an insulating film, the elementsare integrally united by the application of heat and pressure, andscribing is subsequently carried out in the thickness direction.

JP 2002-134570 A examines a method of manufacturing an anisotropicconductive film which involves electroforming conductive columns using aresist and a mask, then pouring an insulating material in the columnsand solidifying the insulating material.

JP 03-182081 A discloses “a method of manufacturing an electricallyconnecting member having a retaining body made of an electricallyinsulating material and a plurality of conductive elements provided in amutually insulating state within the retaining body, wherein an end ofeach conductive element is exposed on a side of the retaining body andthe other end of each conductive element is exposed on the other side ofthe retaining body, the method comprising:

a first step of exposing a matrix having a base and an insulating layerwhich, when deposited on the base, forms the retaining body to a highenergy beam from the insulating layer side, thereby removing all of theinsulating layer and part of the base in a plurality of regions so as toform a plurality of holes in the matrix;

a second step of filling the plurality of formed holes with a conductivematerial for forming the conductive elements so as to be flush with thesides of the insulating layer or to protrude from the sides; and a thirdstep of removing the base.” JP 03-182081 A also carries outinvestigations on various materials (e.g., polyimide resins, epoxyresins and silicone resins) as the insulating layer.

However, with the increasing trend in recent years toward higherintegration, electrode (terminal) sizes in electronic components such assemiconductor devices are becoming smaller, the number of electrodes(terminals) is increasing, and the distance between terminals isbecoming tighter. Moreover, there have also appeared electroniccomponents having a surface construction wherein the surface on each ofthe numerous terminals arranged at a tight pitch lies at a position thatis more recessed than the surface of the component itself.

In order to be able to adapt to such electronic components, there hasarisen a need to make the outer diameter (thickness) of the conductivepaths in anisotropic conductive members smaller and to arrange theconductive paths in a tighter pitch.

However, in the methods of manufacturing the anisotropic conductivefilms and electrically connecting members described in the above patentdocuments, it has been very difficult to reduce the size of theconductive paths. A method of controlling the array of the conductivepaths cannot be found out on the order of the tight pitch.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

It is therefore an object of the invention to provide a microstructurethat can be employed as an anisotropic conductive member or an opticaltransmission member which can dramatically increase the density ofconductive paths, be used as inspection connectors and the like forelectronic components such as semiconductor devices even today whenstill higher levels of integration have been achieved, and control thearray of the conductive paths as desired. Another object of theinvention is to provide a method of manufacturing such a microstructure.

Means for Solving the Problems

The inventors have made an intensive study to achieve the above objectsand discovered a manufacturing method in which an aluminum anodized filmis used for the insulating base to control the portions within the filmthrough which micropores are to pass thus enabling the density of theconductive paths to be dramatically increased while controlling thearray itself of the conductive paths, and the invention has beencompleted.

Specifically, the invention provides the following (1) to (15).

(1) A microstructure comprising a base having through micropores at adensity of at least 10⁷ micropores/mm² wherein part of the throughmicropores are filled with other material than a material of the base.

(2) The microstructure according to (1), wherein the base is aninsulating base.

(3) The microstructure according to (1) or (2), wherein the basecomprises alumina.

(4) The microstructure according to any one of (1) to (3), wherein thethrough micropores are in a straight tube shape.

(5) The microstructure according to any one of (1) to (4), wherein thethrough micropores have a degree of ordering as defined by formula (i):

Degree of ordering (%)=B/A×100  (i)

(wherein A represents a total number of through micropores in ameasurement region, and B represents a number of specific throughmicropores in the measurement region for which, when a circle is drawnso as to be centered on a center of gravity of a specific throughmicropore and so as to be of a smallest radius that is internallytangent to an edge of another through micropore, the circle includescenters of gravity of six through micropores other than the specificthrough micropore) of at least 50%.

(6) The microstructure according to any one of (1) to (5), wherein theother material than the material of the base filled into the throughmicropores are exposed at surfaces of the base.

(7) The microstructure according to any one of (1) to (5), wherein theother material than the material of the base filled into the throughmicropores are protruded from surfaces of the base.

(8) The microstructure according to any one of (1) to (7), wherein thematerial filled into the through micropores is an electricallyconductive material.

(9) The microstructure according to any one of (1) to (8), wherein thethrough micropores have a diameter of 10 to 1000 nm.

(10) A method of manufacturing the microstructure according to any oneof (3) to (9), wherein an aluminum substrate is subjected at least to,in order,

a treatment (A) for anodizing the aluminum substrate to form an oxidefilm having micropores;

a treatment (B) for removing aluminum from the oxide film obtained bythe treatment (A);

a treatment (C) for perforating part of the micropores present in theoxide film from which the aluminum was removed by the treatment (B); and

a treatment (D) for filling the part of the micropores that wereperforated by the treatment (C) with a different material from an oxidefilm material.

(11) The microstructure manufacturing method according to (10), wherein,in order to perforate the part of the micropores present in the oxidefilm in the treatment (C), the treatment (C) comprises at least atreatment (C′) which comprises forming a pattern which is insoluble orhardly soluble in an acid or an alkali on a surface of the oxide filmafter removal of the aluminum, and dissolving portions other than thepattern in the oxide film by using the acid or the alkali to make themicropores formed in the portions other than the pattern in the oxidefilm extend through the oxide film.

(12) The microstructure manufacturing method according to (11), whereinthe treatment (C′) comprises at least a treatment (C′-1) which comprisesforming a photosensitive layer in which solubility with respect to theacid or the alkali changes in response to light on the surface of theoxide film after the removal of the aluminum, irradiating thephotosensitive layer with light beams and dissolving the photosensitivelayer by using the acid or the alkali to form the pattern which isinsoluble or hardly soluble in the acid or the alkali on the surface ofthe oxide film after the removal of the aluminum.

(13) The microstructure manufacturing method according to (11), whereinthe treatment (C′) comprises at least a treatment (C′-2) which comprisesforming a thermosensitive layer in which solubility with respect to theacid or the alkali changes in response to heat on the surface of theoxide film after the removal of the aluminum, heating thethermosensitive layer and dissolving the thermosensitive layer by usingthe acid or the alkali to form the pattern which is insoluble or hardlysoluble in the acid or the alkali on the surface of the oxide film afterthe removal of the aluminum.

(14) The microstructure manufacturing method according to any one of(10) to (13), wherein, in the treatment (D), the different material fromthe oxide film material filled into the micropores that were made toextend through the oxide film by the treatment (C) is an electricallyconductive material.

(15) The microstructure manufacturing method according to (14), wherein,in the treatment (D), the micropores that were made to extend throughthe oxide film by the treatment (C) are filled with the electricallyconductive material by electrolytic plating.

EFFECTS OF THE INVENTION

As shown below, the microstructure of the invention can be preferablyused as an anisotropic conductive member. The anisotropic conductivemember using the microstructure of the invention dramatically increasesthe conductive path density and, even today when still higher levels ofintegration have been achieved, can be used as inspection connectors andthe like for electronic components such as semiconductor devices.

The anisotropic conductive member using the microstructure of theinvention have a large number of conductive paths connected to theelectrode (pads) of an electronic component and the pressure isdispersed, and therefore damage to the electrode can be reduced. Sincethe large number of conductive paths are connected to (in contact with)the single electrode, the influence on the whole confirmation of theconductivity is minimized even in the event of failure in part of theconductive paths. In addition, the load on the positioning of anevaluation circuit board can be considerably reduced.

Furthermore, the method of manufacturing a microstructure according tothe invention is capable of controlling the conductive paths as desiredand therefore this invention can be applied to the optical transmissionmaterials, graphic materials and various other devices and is veryuseful.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are simplified views showing a preferred embodiment ofan anisotropic conductive member of the invention; FIG. 1A being a frontview and FIG. 1B being a cross-sectional view taken along the line IB-IBof FIG. 1A.

FIGS. 2A and 2B are diagrams illustrating a method for computing thedegree of ordering of micropores.

FIGS. 3A to 3D are schematic end views for illustrating anodizingtreatment in the manufacturing method of the invention.

FIGS. 4A to 4D are schematic end views for illustrating metal fillingtreatment and other treatments in the manufacturing method of theinvention.

FIG. 5 is an SEM image of a surface profile after pattern imageformation and removal of the bottom of an anodized film.

DESCRIPTION OF SYMBOLS

-   -   1 Microstructure    -   2 Insulating base    -   2 a, 2 b Surface of the insulating base    -   3, 4 Through micropore    -   5 Conductive path    -   6 a, 6 b Protrusion    -   7 Thickness of the insulating base    -   8 Width between neighboring conductive paths    -   9 Diameter of the conductive path    -   10 Center-to-center distance (pitch) between neighboring        conductive paths    -   12 Aluminum substrate    -   14 a, 14 b, 14 c, 14 d Anodized film    -   16 a, 16 b, 16 c, 16 d Micropore    -   18 a, 18 b, 18 c, 18 d Barrier layer    -   20 Insulating base    -   21 Microstructure    -   101, 102, 104, 105, 107, 108 Micropore    -   103, 106, 109 Circle

BEST MODE FOR CARRYING OUT THE INVENTION

The microstructure and its manufacturing method according to theinvention are described below in detail.

The microstructure of the invention is one comprising a base havingthrough micropores at a density of at least 10⁷ micropores/mm² and partof the through micropores are filled with other material than the basematerial. In cases where the through micropores are filled with anelectrically conductive material, the microstructure can be used as theanisotropic conductive member in which the electrically conductivematerial makes up the conductive paths.

In cases where the microstructure of the invention is used as theanisotropic conductive member, the base should be an insulating base andthe through micropores should be in a straight tube shape.

Next, the case in which the microstructure of the invention is used asthe anisotropic conductive member is described with reference to FIG. 1.

FIG. 1 shows simplified views showing a preferred embodiment of amicrostructure of the invention. FIG. 1A is a front view and FIG. 1B isa cross-sectional view taken along the line IB-IB of FIG. 1A.

A microstructure 1 of the invention comprises an insulating base 2 whichhas straight tube-shaped through micropores 3, 4 at a density of atleast 10⁷ micropores/mm². The straight tube-shaped through micropores 3,4 refer to those having axes substantially parallel (parallel in FIG. 1)to the thickness direction Z of the insulating base 2 and also havingdiameters substantially identical in the axial direction. The expression“through micropores 3, 4 having axes substantially parallel to thethickness direction Z of the insulating base 2″ refers to those havingan angular deviation with respect to the thickness direction Z of theinsulating base 2, of not more than 10°, preferably not more than 5° andmore preferably not more than 3°. The expression “through micropores 3,4 having diameters substantially identical in the axial direction”refers to those having a diameter deviation ΔD as represented by thefollowing formula of not more than 10%, preferably not more than 7% andmore preferably not more than 5%.

ΔD=(D _(max) −D _(min))/D _(ave)×100(%)

D_(max) is the maximum diameter of the through micropores 3, 4; D_(min)is the minimum diameter of the through micropores 3, 4;D_(ave) is the average diameter of the through micropores 3, 4.

In the microstructure 1 of the invention, part of the through micropores3, 4 (through micropores 3 in FIG. 1) are filled with an electricallyconductive material, thus forming conductive paths 5. In other words,the microstructure 1 shown in FIG. 1 includes the plurality ofconductive paths 5 formed by filling the through micropores 3 with theelectrically conductive material and a plurality of paths formed fromthe through micropores 4 into which no electrically conductive materialis filled.

Each conductive path 5 is required to have one end exposed at onesurface of the insulating base 2 and the other end exposed at the othersurface of the insulating base 2. In other words, in cases where themicrostructure 1 of the invention is used as the anisotropic conductivemember, the electrically conductive material filled into the throughmicropores 3 is required to be exposed at the surfaces of the insulatingbase 2. As shown in FIG. 1B, the electrically conductive material filledinto the through micropores 3 are preferably protruded from surfaces 2 aand 2 b of the insulating base. More specifically, each conductive path5 preferably has one end protruded from the surface 2 a on one side ofthe insulating base 2 and the other end protruded from the surface 2 bon the other side of the insulating base 2. In other words, both theends of each conductive path 5 preferably have protrusions 6 a and 6 bprotruded from the main surfaces 2 a and 2 b of the insulating base,respectively.

Next, the materials and dimensions of the respective components of themicrostructure are described.

[Insulating Base]

The insulating base 2 making up the microstructure 1 of the inventionhas the through micropores 3, 4 at a density of at least 10⁷micropores/mm². The insulating base should have an electric resistivityof 10¹⁴ Ω·cm which is equivalent to that of an insulating base (e.g., athermoplastic elastomer) making up a conventionally known anisotropicconductive film.

The insulating base is not particularly limited as long as theabove-described requirements are satisfied. However, alumina ispreferred because the insulating base can be easily manufactured byusing the microstructure manufacturing method of the invention to bedescribed later.

From the viewpoint that the density of the through micropores can beincreased, the through micropores in the insulating base making up themicrostructure of the invention preferably have a degree of ordering, asdefined by formula (i):

Degree of ordering (%)=B/A×100  (i)

(wherein A represents the total number of through micropores in ameasurement region, and B represents the number of specific throughmicropores in the measurement region for which, when a circle is drawnso as to be centered on the center of gravity of a specific throughmicropore and so as to be of the smallest radius that is internallytangent to the edge of another through micropore, the circle includesthe centers of gravity of six through micropores other than the specificthrough micropore) of at least 50%.

FIG. 2 shows diagrams illustrating the method for computing the degreeof ordering of the through micropores. Above formula (1) is explainedmore fully below in conjunction with FIG. 2.

In the case of a first through micropore 101 shown in FIG. 2A, when acircle 103 is drawn so as to be centered on the center of gravity of thefirst through micropore 101 and so as to be of the smallest radius thatis internally tangent to the edge of another through micropore(inscribed in a second through micropore 102), the interior of thecircle 3 includes the centers of gravity of six through micropores otherthan the first through micropore 101. Therefore, the first throughmicropore 101 is included in B.

In the case of another first through micropore 104 shown in FIG. 2B,when a circle 106 is drawn so as to be centered on the center of gravityof the first through micropore 104 and so as to be of the smallestradius that is internally tangent to the edge of another throughmicropore (inscribed in a second through micropore 105), the interior ofthe circle 106 includes the centers of gravity of five throughmicropores other than the first through micropore 104. Therefore, thefirst through micropore 104 is not included in B.

In the case of yet another first through micropore 107 shown in FIG. 2B,when a circle 109 is drawn so as to be centered on the center of gravityof the first through micropore 107 and so as to be of the smallestradius that is internally tangent to the edge of another throughmicropore (inscribed in a second through micropore 108), the interior ofthe circle 109 includes the centers of gravity of seven throughmicropores other than the first through micropore 107. Therefore, thefirst through micropore 107 is not included in B.

The insulating base 2 making up the microstructure 1 of the inventionpreferably has a thickness (as shown in FIG. 1B by the reference symbol7) of from 30 to 300 μm, and more preferably from 50 to 100 μm. At aninsulating base thickness within the foregoing range, the insulatingbase can be handled with ease.

Moreover, in the insulating base 2 making up the microstructure 1 of theinvention, the width between the conductive paths 5 (i.e., width betweenthe neighboring through micropores 3 filled with an electricallyconductive material or portion represented in FIG. 1B by the referencesymbol 8) is preferably at least 10 nm, more preferably from 20 to 100nm, and even more preferably from 20 to 50 nm. At a width between thethrough micropores 3 of the insulating base filled with the electricallyconductive within the foregoing range, the insulating base functionsfully as an insulating barrier.

[Electrically Conductive Material]

In the microstructure 1 of the invention, the electrically conductivematerial to be filled into the through micropores 3 is not particularlylimited as long as the material used has an electric resistivity of notmore than 10³ Ω·cm. Illustrative examples of the electrically conductivematerial that may be preferably used include gold (Au), silver (Ag),copper (Cu), aluminum (Al), magnesium (Mg), and nickel (Ni).

Of these, in terms of electric conductivity, copper, gold, aluminum andnickel are preferred, copper and gold being more preferred.

In terms of cost, it is more preferable to use other materials than gold(e.g., copper) as the electrically conductive material to be filled intothe through micropores 3 and to use gold only for forming the surfacesof the paths exposed at or protruded from both the surfaces of theinsulating base 2 (hereinafter also referred to as “end faces”).

In the microstructure 1 of the invention, all the through micropores 3may be filled with the same or different electrically conductivematerials. The front and back sides of each through micropore 3 may befilled with different electrically conductive materials.

In the microstructure 1 of the invention, the diameter of the conductivepaths 5, (i.e., diameter of the through micropores 3 filled with theelectrically conductive material or portion represented in FIG. 1B bythe reference symbol 9) is preferably from 20 to 400 nm, more preferablyfrom 40 to 200 nm, and even more preferably from 50 to 100 nm. At adiameter of the conductive paths within the foregoing range, whenelectrical signals are passed through the conductive paths, sufficientresponses can be obtained, thus enabling more preferable use of themicrostructure 1 of the invention as an inspection connector forelectronic components.

In the microstructure 1 of the invention, when both the ends of theconductive path 5 protrude from both the surfaces 2 a and 2 b of theinsulating base 2, that is, when the electrically conductive materialfilled into the through micropores 3 protrudes from both the surfaces ofthe insulating base 2, the protrusions (in FIG. 1B, the portionsrepresented by the reference symbols 6 a and 6 b; also referred to belowas “bumps”) have a height of preferably from 1 to 100 nm, and morepreferably from 5 to 50 nm. At a bump height in this range, connectivitywith the electrode (pads) on an electronic component improves.

In the microstructure 1 of the invention, the conductive paths 5, thatis, the through micropores 3 into which the electrically conductivematerial is filled are insulated from each other by the insulating base2 and their density is at least 10⁷ micropores/mm², preferably at least5×10⁷ micropores/mm², and more preferably at least 10⁸ micropores/mm².

At a density of the through micropores 3 within the foregoing range, themicrostructure of the invention can be used as inspection connectors andthe like for electronic components such as semiconductor devices eventoday when still higher levels of integration have been achieved.

In the microstructure 1 of the invention, the center-to-center distancebetween neighboring conductive paths 5 (i.e., center-to-center distancebetween neighboring through micropores 3 or the portion represented inFIG. 1 by the reference symbol 10; also referred to below as the“pitch”) is preferably from 20 to 500 nm, more preferably from 40 to 200nm, and even more preferably from 50 to 140 nm. At a pitch in theforegoing range, a balance between the diameter of the conductive pathsand the width between the conductive paths (insulating barrierthickness) is easily achieved.

In cases where the microstructure 1 of the invention is used as theanisotropic conductive member, as described above, it is preferred forthe insulating base 2 to have a thickness of 30 to 300 μm, and for theconductive paths 5, that is, the through micropores 3 into which theelectrically conductive material is filled to have a diameter of from 20to 400 nm, because electrical conduction can be confirmed at a highdensity while keeping high insulating properties.

In cases where the microstructure 1 of the invention is used as theanisotropic conductive member, the through micropores 4 are preferablyarrayed in a pattern as shown in FIG. 1 from the viewpoint that wiringof a desired pattern can be connected.

The through micropores 4 preferably have a diameter of 10 to 1000 nm,more preferably 20 to 850 nm and even more preferably 30 to 700 nm interms of increasing the strength of the microstructure.

The microstructure of the invention which uses alumina for the base canbe obtained by the inventive method of manufacturing microstructures tobe described later. This method is also hereinafter referred to simplyas the “inventive manufacturing method.”

The invention provides a method of manufacturing a microstructure,wherein an aluminum substrate is subjected at least to, in order,

treatment (A) in which a micropore-bearing oxide film is formed byanodization;treatment (B) in which aluminum is removed from the oxide film obtainedby treatment (A);treatment (C) in which part of the micropores present in the oxide filmfrom which the aluminum has been removed by treatment (B) are made toextend through the oxide film; andtreatment (D) in which the micropores which were made to extend throughthe oxide film by treatment (C) are filled with other material than theoxide film material.

Next, an aluminum substrate that may be used in the inventivemanufacturing method, and each treatment step carried out on thealuminum substrate are described in detail.

[Aluminum Substrate]

The aluminum substrate that may be used in the inventive manufacturingmethod is not subject to any particular limitation. Illustrativeexamples include pure aluminum plate; alloy plates composed primarily ofaluminum and containing trace amounts of other elements; substrates madeof low-purity aluminum (e.g., recycled material) on which high-purityaluminum has been vapor-deposited; substrates such as silicon wafers,quartz or glass whose surface has been covered with high-purity aluminumby a process such as vapor deposition or sputtering; and resinsubstrates on which aluminum has been laminated.

Of the aluminum substrate of the invention, the surface on which ananodized film is to be formed by the treatment (A) to be described belowhas an aluminum purity of preferably at least 99.5 wt %, more preferablyat least 99.9 wt % and even more preferably at least 99.99 wt %. It ispreferable for the aluminum purity to fall within the above range,because the array of the micropores is well ordered.

In the practice of the invention, the surface of the aluminum substrateon which the subsequently described treatment (A) is to be carried outis preferably subjected beforehand to degreasing treatment andmirror-like finishing treatment.

<Heat Treatment>

Heat treatment is preferably carried out at a temperature of from 200 to350° C. for a period of about 30 seconds to about 2 minutes. Such heattreatment improves the orderliness of the micropore array formed by thesubsequently described treatment (A).

Following heat treatment, it is preferable to rapidly cool the aluminumsubstrate. The method of cooling is exemplified by a method involvingdirect immersion of the aluminum substrate in water or the like.

<Degreasing Treatment>

Degreasing treatment is carried out with a suitable substance such as anacid, alkali or organic solvent so as to dissolve and remove organicsubstances, including dust, grease and resins, adhering to the aluminumsubstrate surface, and thereby prevent defects due to organic substancesfrom arising in each of the subsequent treatments.

Preferred degreasing methods include the following: a method in which anorganic solvent such as an alcohol (e.g., methanol), ketone (e.g.,methyl ethyl ketone), petroleum benzin or volatile oil is contacted withthe surface of the aluminum substrate at ambient temperature (organicsolvent method); a method in which a liquid containing a surfactant suchas soap or a neutral detergent is contacted with the surface of thealuminum substrate at a temperature of from ambient temperature to 80°C., after which the surface is rinsed with water (surfactant method); amethod in which an aqueous sulfuric acid solution having a concentrationof 10 to 200 g/L is contacted with the surface of the aluminum substrateat a temperature of from ambient temperature to 70° C. for a period of30 to 80 seconds, following which the surface is rinsed with water; amethod in which an aqueous solution of sodium hydroxide having aconcentration of 5 to 20 g/L is contacted with the surface of thealuminum substrate at ambient temperature for about 30 seconds whileelectrolysis is carried out by passing a direct current through thealuminum substrate surface as the cathode at a current density of 1 to10 A/dm², following which the surface is contacted with an aqueoussolution of nitric acid having a concentration of 100 to 500 g/L andthereby neutralized; a method in which any of various known anodizingelectrolytic solutions is contacted with the surface of the aluminumsubstrate at ambient temperature while electrolysis is carried out bypassing a direct current at a current density of 1 to 10 A/dm² throughthe aluminum substrate surface as the cathode or by passing analternating current through the aluminum substrate surface as thecathode; a method in which an aqueous alkali solution having aconcentration of 10 to 200 g/L is contacted with the surface of thealuminum substrate at 40 to 50° C. for 15 to 60 seconds, following whichan aqueous solution of nitric acid having a concentration of 100 to 500g/L is contacted with the surface and thereby neutralized; a method inwhich an emulsion prepared by mixing a surfactant, water and the likeinto an oil such as gas oil or kerosene is contacted with the surface ofthe aluminum substrate at a temperature of from ambient temperature to50° C., following which the surface is rinsed with water (emulsiondegreasing method); and a method in which a mixed solution of, forexample, sodium carbonate, phosphates and surfactant is contacted withthe surface of the aluminum substrate at a temperature of from ambienttemperature to 50° C. for 30 to 180 seconds, following which the surfaceis rinsed with water (phosphate method).

Of these, the organic solvent method, surfactant method, emulsiondegreasing method and phosphate method are preferred from the standpointof removing grease from the aluminum surface while causing substantiallyno aluminum dissolution.

Known degreasers may be used in degreasing treatment. For example,degreasing treatment may be carried out using any of variouscommercially available degreasers by the prescribed method.

<Mirror-Like Finishing Treatment>

Mirror-like finishing treatment is carried out to eliminate surfaceasperities of the aluminum substrate and improve the uniformity andreproducibility of particle-forming treatment using, for example,electrodeposition. Exemplary surface asperities of the aluminumsubstrate include rolling streaks formed during rolling of the aluminumsubstrate which requires a rolling step for its manufacture.

In the practice of the invention, mirror-like finishing treatment is notsubject to any particular limitation, and may be carried out using anysuitable method known in the art. Examples of suitable methods includemechanical polishing, chemical polishing, and electrolytic polishing.

Illustrative examples of suitable mechanical polishing methods includepolishing with various commercial abrasive cloths, and methods thatcombine the use of various commercial abrasives (e.g., diamond, alumina)with buffing. More specifically, a method which is carried out with anabrasive while changing over time the abrasive used from one havingcoarser particles to one having finer particles is appropriatelyillustrated. In such a case, the final abrasive used is preferably onehaving a grit size of 1500. In this way, a glossiness of at least 50%(in the case of rolled aluminum, at least 50% in both the rollingdirection and the transverse direction) can be achieved.

Examples of chemical polishing methods include various methods mentionedin the 6th edition of Aluminum Handbook (Japan Aluminum Association,2001), pp. 164-165.

Preferred examples include phosphoric acid/nitric acid method, Alupol Imethod, Alupol V method, Alcoa R5 method, H₃PO₄—CH₃COOH—Cu method andH₃PO₄—HNO₃—CH₃COOH method. Of these, the phosphoric acid/nitric acidmethod, the H₃PO₄—CH₃COOH—Cu method and the H₃PO₄—HNO₃—CH₃COOH methodare especially preferred.

With chemical polishing, a glossiness of at least 70% (in the case ofrolled aluminum, at least 70% in both the rolling direction and thetransverse direction) can be achieved.

Examples of electrolytic polishing methods include various methodsmentioned in the 6th edition of Aluminum Handbook (Japan AluminumAssociation, 2001), pp. 164-165; the method described in U.S. Pat. No.2,708,655; and the method described in Jitsumu Hyomen Gijutsu (Practiceof Surface Technology), Vol. 33, No. 3, pp. 32-38 (1986).

With electrolytic polishing, a glossiness of at least 70% (in the caseof rolled aluminum, at least 70% in both the rolling direction and thetransverse direction) can be achieved.

These methods may be suitably combined and used. In an illustrativemethod that may be preferably used, mechanical polishing which iscarried out by changing the abrasive over time from one having coarserparticles to one having finer particles is followed by electrolyticpolishing.

Mirror-like finishing treatment enables a surface having, for example, amean surface roughness R_(a) of 0.1 μm or less and a glossiness of atleast 50% to be obtained. The mean surface roughness R_(a) is preferably0.03 μm or less, and more preferably 0.02 μm or less. The glossiness ispreferably at least 70%, and more preferably at least 80%.

The glossiness is the specular reflectance which can be determined inaccordance with JIS Z8741-1997 (Method 3: 60° Specular Gloss) in adirection perpendicular to the rolling direction. Specifically,measurement is carried out using a variable-angle glossmeter (e.g.,VG-1D, manufactured by Nippon Denshoku Industries Co., Ltd.) at an angleof incidence/reflection of 60° when the specular reflectance is 70% orless, and at an angle of incidence/reflection of 20° when the specularreflectance is more than 70%.

(A) Treatment in which a Micropore-Bearing Oxide Film is Formed byAnodization

In treatment (A), the aluminum substrate is anodized to form amicropore-bearing oxide film at the surface of the aluminum substrate.

Conventionally known methods may be used for anodizing treatment in themanufacturing method of the invention, but a self-ordering method to bedescribed below is preferably used because the insulating base is ananodized film in an aluminum substrate which has micropores arrayed soas to have a degree of ordering as defined by formula (i) of preferablyat least 50%.

The self-ordering method is a method which enhances the orderliness byusing the regularly arranging nature of micropores in an anodized filmand eliminating factors that may disturb an orderly arrangement.Specifically, an anodized film is formed on high-purity aluminum at avoltage appropriate for the type of electrolytic solution and at a lowspeed over an extended period of time (e.g., from several hours to wellover ten hours).

In this method, because the micropore size is dependent on the voltage,to some degree it is possible to obtain the desired micropore size bycontrolling the voltage.

To form micropores by the self-ordering method, the subsequentlydescribed anodizing treatment (a) should be carried out. However,micropore formation is preferably carried out by a process in which thesubsequently described anodizing treatment (a), film removal treatment(b) and re-anodizing treatment (c) are carried out in this order(self-ordering method I), or a process in which the subsequentlydescribed anodizing treatment (d) and oxide film dissolution treatment(e) are carried out in this order at least once (self-ordering methodII).

Next, the respective treatments in the self-ordering method I andself-ordering method II in the preferred embodiments are described indetail.

[Self-Ordering Method I]

<Anodizing Treatment (a)>

The average flow velocity of electrolytic solution in anodizingtreatment (a) is preferably from 0.5 to 20.0 m/min, more preferably from1.0 to 15.0 m/min, and even more preferably from 2.0 to 10.0 m/min. Bycarrying out anodizing treatment (a) at the foregoing flow velocity, auniform and high degree of ordering can be achieved.

The method for causing the electrolytic solution to flow under the aboveconditions is not subject to any particular limitation. For example, amethod involving the use of a common agitator such as a stirrer may beemployed. The use of a stirrer in which the stirring speed can becontrolled with a digital display is particularly desirable because itenables the average flow velocity to be regulated. An example of such astirrer is the Magnetic Stirrer HS-50D (manufactured by As OneCorporation).

Anodizing treatment (a) may be carried out by, for example, a method inwhich current is passed through the aluminum substrate as the anode in asolution having an acid concentration of from 1 to 10 wt %.

The solution used in anodizing treatment (a) is preferably an acidsolution. A solution of sulfuric acid, phosphoric acid, malonic acid,chromic acid, oxalic acid, sulfamic acid, benzenesulfonic acid,amidosulfonic acid, glycolic acid, tartaric acid, malic acid or citricacid is more preferred. Of these, a solution of sulfuric acid,phosphoric acid, oxalic acid or malonic acid is especially preferred.These acids may be used singly or as combinations of two or morethereof.

The anodizing treatment (a) conditions vary depending on theelectrolytic solution employed, and thus cannot be strictly specified.However, the following conditions are generally preferred: anelectrolytic solution concentration of from 0.1 to 20 wt %, a solutiontemperature of from −10 to 30° C., a current density of from 0.01 to 20A/dm², a voltage of from 3 to 300 V, and an electrolysis time of from0.5 to 30 hours. An electrolytic solution concentration of from 0.5 to15 wt %, a solution temperature of from −5 to 25° C., a current densityof from 0.05 to 15 A/dm², a voltage of from 5 to 250 V, and anelectrolysis time of from 1 to 25 hours are more preferred. Anelectrolytic solution concentration of from 1 to 10 wt %, a solutiontemperature of from 0 to 20° C., a current density of from 0.1 to 10A/dm², a voltage of from 10 to 200 V, and an electrolysis time of from 2to 20 hours are even more preferred.

The treatment time in anodizing treatment (a) is preferably from 0.5minute to 16 hours, more preferably from 1 minute to 12 hours, and evenmore preferably from 2 minutes to 8 hours.

Aside from being carried out at a constant voltage, anodizing treatment(a) may be carried out using a method in which the voltage isintermittently or continuously varied. In such cases, it is preferableto have the voltage gradually decrease. It is possible in this way tolower the resistance of the anodized film, bringing about the formationof small micropores in the anodized film. As a result, this approach ispreferable for improving uniformity, particularly when sealing issubsequently carried out by electrodeposition treatment.

In the invention, the anodized film formed by such anodizing treatment(a) preferably has a thickness of 1 to 300 μm, more preferably 5 to 150μm, and even more preferably 10 to 100 μm.

In the invention, the anodized film formed by such anodizing treatment(a) has an average micropore density of preferably from 50 to 1,500micropores/μm².

It is preferable for the micropores to have a surface coverage of from20 to 50%.

The surface coverage of the micropores is defined here as the ratio ofthe total surface area of the micropore openings to the surface area ofthe aluminum surface.

<Film Removal Treatment (b)>

In film removal treatment (b), the anodized film formed at the surfaceof the aluminum substrate by the above-described anodizing treatment (a)is dissolved and removed.

The subsequently described perforation step may be carried outimmediately after forming an anodized film at the surface of thealuminum substrate by the above-described anodizing treatment (a).However, after the anodizing treatment (a), it is preferable toadditionally carry out film removal treatment (b) and the subsequentlydescribed re-anodizing treatment (c) in this order, followed by thesubsequently described perforation step.

Given that the orderliness of the anodized film increases as thealuminum substrate is approached, by using this film removal treatment(b) to remove the anodized film that has been formed in (a), the lowerportion of the anodized film remaining at the aluminum substrate emergesat the surface, affording an orderly array of pits. Therefore, in filmremoval treatment (b), aluminum is not dissolved; only the anodized filmcomposed of alumina (aluminum oxide) is dissolved.

The alumina dissolving solution is preferably an aqueous solutioncontaining at least one substance selected from the group consisting ofchromium compounds, nitric acid, phosphoric acid, zirconium compounds,titanium compounds, lithium salts, cerium salts, magnesium salts, sodiumhexafluorosilicate, zinc fluoride, manganese compounds, molybdenumcompounds, magnesium compounds, barium compounds, and uncombinedhalogens.

Illustrative examples of chromium compounds include chromium (III) oxideand chromium (VI) oxide.

Examples of zirconium compounds include zirconium ammonium fluoride,zirconium fluoride and zirconium chloride.

Examples of titanium compounds include titanium oxide and titaniumsulfide.

Examples of lithium salts include lithium fluoride and lithium chloride.

Examples of cerium salts include cerium fluoride and cerium chloride.

Examples of magnesium salts include magnesium sulfide.

Examples of manganese compounds include sodium permanganate and calciumpermanganate.

Examples of molybdenum compounds include sodium molybdate.

Examples of magnesium compounds include magnesium fluoride pentahydrate.

Examples of barium compounds include barium oxide, barium acetate,barium carbonate, barium chlorate, barium chloride, barium fluoride,barium iodide, barium lactate, barium oxalate, barium perchlorate,barium selenate, barium selenite, barium stearate, barium sulfite,barium titanate, barium hydroxide, barium nitrate, and hydrates thereof.

Of the above barium compounds, barium oxide, barium acetate and bariumcarbonate are preferred. Barium oxide is especially preferred.

Examples of uncombined halogens include chlorine, fluorine and bromine.

Of the above, the alumina dissolving solution is preferably anacid-containing aqueous solution. Examples of the acid include sulfuricacid, phosphoric acid, nitric acid and hydrochloric acid. A mixture oftwo or more acids is also acceptable.

The acid concentration is preferably at least 0.01 mol/L, morepreferably at least 0.05 mol/L, and even more preferably at least 0.1mol/L. Although there is no particular upper limit in the acidconcentration, in general, the concentration is preferably 10 mol/L orless, and more preferably 5 mol/L or less. A needlessly highconcentration is uneconomical, in addition to which higherconcentrations may result in dissolution of the aluminum substrate.

The alumina dissolving solution has a temperature of preferably −10° C.or higher, more preferably −5° C. or higher, and even more preferably 0°C. or higher. Carrying out treatment using a boiling alumina dissolvingsolution destroys or disrupts the starting points for ordering. Hence,the alumina dissolving solution is preferably used without being boiled.

An alumina dissolving solution dissolves alumina, but does not dissolvealuminum. Here, the alumina dissolving solution may dissolve a verysmall amount of aluminum, so long as it does not dissolve a substantialamount of aluminum.

Film removal treatment (b) is carried out by bringing an aluminumsubstrate at which an anodized film has been formed into contact withthe above-described alumina dissolving solution. Examples of thecontacting method include, but are not limited to, immersion andspraying. Of these, immersion is preferred.

Immersion is a treatment in which the aluminum substrate at which ananodized film has been formed is immersed in the alumina dissolvingsolution. To achieve uniform treatment, it is desirable to carry outstirring at the time of immersion treatment.

The immersion treatment time is preferably at least 10 minutes, morepreferably at least 1 hour, even more preferably at least 3 hours, andmost preferably at least 5 hours.

<Re-Anodizing Treatment (c)>

An anodized film having micropores with an even higher degree ofordering can be formed by carrying out anodizing treatment once againafter the anodized film is removed by the film removal treatment (b) toform well-ordered pits on the surface of the aluminum substrate.

Re-anodizing treatment (c) may be carried out using a method known inthe art, although it is preferably carried out under the same conditionsas the above-described anodizing treatment (a).

Alternatively, suitable use may be made of a method in which the currentis repeatedly turned on and off while keeping the dc voltage constant,or a method in which the current is repeatedly turned on and off whileintermittently varying the dc voltage. Because these methods result inthe formation of small micropores in the anodized film, they arepreferable for improving uniformity, particularly when sealing is to becarried out by electrodeposition treatment.

When re-anodizing treatment (c) is carried out at a low temperature, thearray of micropores is well-ordered and the pore size is uniform.

On the other hand, by carrying out re-anodizing treatment (c) at arelatively high temperature, the micropore array may be disrupted or thevariance in pore size may be set within a given range. The variance inpore size may also be controlled by means of the treatment time.

In the practice of the invention, the anodized film formed by suchre-anodizing treatment (c) has a thickness of preferably from 30 to1,000 μm, and more preferably from 50 to 500 μm.

Moreover, in the invention, the micropores formed in the anodized filmby such re-anodizing treatment (c) have a diameter of preferably from0.01 to 0.5 μm and more preferably from 0.02 to 0.1 μm.

The average micropore density is preferably at least 10⁷ micropores/mm².

In the self-ordering method I, in place of the above-described anodizingtreatment (a) and film removal treatment (b), use may be made of, forexample, a physical method, a particle beam method, a block copolymermethod or a resist patterning/exposure/etching process to form pits asstarting points for micropore formation by the above-describedre-anodizing treatment (c).

<Physical Method>

Physical methods are exemplified by methods which use imprinting(transfer methods and press patterning methods in which a plate or rollhaving projections thereon is pressed against the aluminum substrate toform depressions on the substrate). A specific example is a method inwhich a plate having numerous projections on a surface thereof ispressed against the aluminum surface, thereby forming depressions. Forexample, the method described in JP 10-121292 A may be used.

Another example is a method in which polystyrene spheres are denselyarranged on the aluminum surface, SiO₂ is vapor-deposited onto thespheres, then the polystyrene spheres are removed and the substrate isetched using the vapor-deposited SiO₂ as the mask, thereby formingdepressions.

<Particle Beam Method>

In a particle beam method, depressions are formed by irradiating thealuminum surface with a particle beam. This method has the advantagethat the positions of the depressions can be freely controlled.

Examples of the particle beam include a charged particle beam, a focusedion beam (FIB), and an electron beam.

An example of the particle beam method that may be used is the methoddescribed in JP 2001-105400 A.

<Block Copolymer Method>

The block copolymer method involves forming a block copolymer layer onthe aluminum surface, forming an islands-in-the-sea structure in theblock copolymer layer by thermal annealing, then removing the islandcomponents to form depressions.

An example of the block copolymer method that may be used is the methoddescribed in JP 2003-129288 A.

<Resist Patterning/Exposure/Etching Process>

In a resist patterning/exposure/etching process, resist on the surfaceof an aluminum plate is exposed and developed by photolithography orelectron-beam lithography to form a resist pattern. The resist is thenetched, forming depressions which pass entirely through the resist tothe aluminum surface.

[Self-Ordering Method II]

<First Step: Anodizing Treatment (d)>

Conventionally known electrolytic solutions may be used in anodizingtreatment (d) but the orderliness of the pore array can be considerablyimproved by carrying out, under conditions of direct current andconstant voltage, anodization using an electrolytic solution in whichthe parameter R represented by general formula (ii) wherein A is thefilm-forming rate during application of current and B is the filmdissolution rate during non-application of current satisfies 160≦R≦200,preferably 170≦R≦190 and most particularly 175≦R≦185.

R=A [nm/s]/(B [nm/s]×voltage applied [V])  (ii)

As in the above-described anodizing treatment (a), the average flowvelocity of electrolytic solution in anodizing treatment (d) ispreferably from 0.5 to 20.0 m/min, more preferably from 1.0 to 15.0m/min, and even more preferably from 2.0 to 10.0 m/min. By carrying outanodizing treatment (d) at the foregoing flow velocity, a uniform andhigh degree of ordering can be achieved.

As in the above-described anodizing treatment (a), the method forcausing the electrolytic solution to flow under the above conditions isnot subject to any particular limitation. For example, a methodinvolving the use of a common agitator such as a stirrer may beemployed. The use of a stirrer in which the stirring speed can becontrolled with a digital display is particularly desirable because itenables the average flow velocity to be regulated. An example of such astirrer is the Magnetic Stirrer HS-50D (manufactured by As OneCorporation).

The anodizing treatment solution preferably has a viscosity at 25° C.and 1 atm of 0.0001 to 100.0 Pa·s and more preferably 0.0005 to 80.0Pa·s. By carrying out anodizing treatment (d) using the electrolyticsolution having the foregoing viscosity, a uniform and high degree ofordering can be achieved.

The electrolytic solution used in anodizing treatment (d) may be anacidic solution or an alkaline solution, but an acidic electrolyticsolution is advantageously used in terms of improving the circularity ofthe pores.

More specifically, as in the above-described anodizing treatment (a), asolution of hydrochloric acid, sulfuric acid, phosphoric acid, chromicacid, oxalic acid, glycolic acid, tartaric acid, malic acid, citricacid, sulfamic acid, benzenesulfonic acid, amidosulfonic acid, glycolicacid, tartaric acid, malic acid, or citric acid is more preferred. Ofthese, a solution of sulfuric acid, phosphoric acid or oxalic acid isespecially preferred. These acids may be used singly or as combinationsof two or more thereof by adjusting the parameter in the calculatingformula represented by general formula (ii) as desired.

The anodizing treatment (d) conditions vary depending on theelectrolytic solution employed, and thus cannot be strictly specified.However, as in the above-described anodizing treatment (a), thefollowing conditions are generally preferred: an electrolytic solutionconcentration of from 0.1 to 20 wt %, a solution temperature of from −10to 30° C., a current density of from 0.01 to 20 A/dm², a voltage of from3 to 500 V, and an electrolysis time of from 0.5 to 30 hours. Anelectrolytic solution concentration of from 0.5 to 15 wt %, a solutiontemperature of from −5 to 25° C., a current density of from 0.05 to 15A/dm², a voltage of from 5 to 250 V, and an electrolysis time of from 1to 25 hours are more preferred. An electrolytic solution concentrationof from 1 to 10 wt %, a solution temperature of from 0 to 20° C., acurrent density of from 0.1 to 10 A/dm², a voltage of from 10 to 200 V,and an electrolysis time of from 2 to 20 hours are even more preferred.

In the practice of the invention, the anodized film formed by suchanodizing treatment (d) has a thickness of preferably from 0.1 to 300μm, more preferably from 0.5 to 150 μm and even more preferably from 1to 100 μm.

In the invention, the anodized film formed by such anodizing treatment(d) has an average micropore density of preferably from 50 to 1,500micropores/μm².

It is preferable for the micropores to have a surface coverage of from20 to 50%.

The surface coverage of the micropores is defined here as the ratio ofthe total surface area of the micropore openings to the surface area ofthe aluminum surface.

As shown in FIG. 3A, as a result of anodizing treatment (d), an anodizedfilm 14 a bearing micropores 16 a is formed at a surface of an aluminumsubstrate 12. A barrier layer 18 a is present on the side of thealuminum substrate 12 from the anodized film 14 a.

<Second Step: Oxide Film Dissolution Treatment (e)>

Oxide film dissolution treatment (e) is a treatment for enlarging thediameter of the micropores present in the anodized film formed by theabove-described anodizing treatment (d) (pore diameter). This treatmentis also referred to as pore diameter enlarging treatment.

Oxide film dissolution treatment (e) is carried out by bringing thealuminum substrate having undergone the above-described anodizingtreatment (d) into contact with the aqueous acid or alkali solution.Examples of the contacting method include, but are not limited to,immersion and spraying. Of these, immersion is preferred.

When oxide film dissolution treatment (e) is to be performed with anaqueous acid solution, it is preferable to use an aqueous solution of aninorganic acid such as sulfuric acid, phosphoric acid, nitric acid orhydrochloric acid, or a mixture thereof. It is particularly preferableto use an aqueous solution containing no chromic acid in terms of itshigh degree of safety. The aqueous acid solution preferably has aconcentration of 1 to 10 wt %. The aqueous acidic solution preferablyhas a temperature of 25 to 60° C.

When oxide film dissolution treatment (e) is to be performed with anaqueous alkali solution, it is preferable to use an aqueous solution ofat least one alkali selected from the group consisting of sodiumhydroxide, potassium hydroxide and lithium hydroxide. The aqueous alkalisolution preferably has a concentration of 0.1 to 5 wt %. The aqueousalkali solution preferably has a temperature of 20 to 35° C.

Specific examples of preferred solutions include a 40° C. aqueoussolution containing 50 g/L of phosphoric acid, a 30° C. aqueous solutioncontaining 0.5 g/L of sodium hydroxide, and a 30° C. aqueous solutioncontaining 0.5 g/L of potassium hydroxide.

The time of immersion in the aqueous acid solution or aqueous alkalisolution is preferably from 8 to 120 minutes, more preferably from 10 to90 minutes and even more preferably from 15 to 60 minutes.

In the oxide film dissolution treatment (e), the amount of enlargementof the pore diameter vary with the conditions of anodizing treatment (d)but the ratio of after to before the treatment is preferably 1.05 to100, more preferably 1.1 to 75 and even more preferably 1.2 to 50.

Oxide film dissolution treatment (e) dissolves the surface of theanodized film 14 a and the interiors of the micropores 16 a (barrierlayer 18 a) as shown in FIG. 3A to obtain an aluminum member having amicropore 16 b-bearing anodized film 14 b on the aluminum substrate 12as shown in FIG. 3B. As in FIG. 3A, a barrier layer 18 b is present onthe side of the aluminum substrate 12 from the anodized film 14 b.

<Third Step: Anodizing Treatment (d)>

In the self-ordering method II, it is preferred to carry out theabove-described anodizing treatment (d) again after the above-describedoxide film dissolution treatment (e).

By carrying out anodizing treatment (d) again, oxidation reaction of thealuminum substrate 12 shown in FIG. 3B proceeds to obtain, as shown inFIG. 3C, an aluminum member which has an anodized film 14 c formed onthe aluminum substrate 12, the anodized film 14 c bearing micropores 16c having a larger depth than the micropores 16 b. As in FIG. 3A, abarrier layer 18 c is present on the side of the aluminum substrate 12from the anodized film 14 c.

<Fourth Step: Oxide Film Dissolution Treatment (e)>

In the self-ordering method II, it is preferred to further carry out theabove-described oxide film dissolution treatment (e) after theabove-described anodizing treatment (d), oxide film dissolutiontreatment (e) and anodizing treatment (d) have been carried out in thisorder.

This treatment enables the treatment solution to enter the micropores todissolve all the film formed by anodizing treatment (d) in the thirdstep, whereby the micropores formed by anodizing treatment (d) in thethird step may have enlarged diameters.

More specifically, oxide film dissolution treatment (e) carried outagain dissolves the interiors of the micropores 16 c on the surface sidefrom inflection points in the anodized film 14 c shown in FIG. 3C toobtain an aluminum member having an anodized film 14 d bearing straighttube-shaped micropores 16 d on the aluminum substrate 12 as shown inFIG. 3D. As in FIG. 3A, a barrier layer 18 d is present on the side ofthe aluminum substrate 12 from the anodized film 14 d.

The amount of enlargement of the pore diameter of the micropores varywith the treatment conditions in anodizing treatment (d) carried out inthe third step but the ratio of after to before the treatment ispreferably 1.05 to 100, more preferably 1.1 to 75 and even morepreferably 1.2 to 50.

The self-ordering method II involves at least one cycle of theabove-described anodizing treatment (d) and oxide film dissolutiontreatment (e). The larger the number of repetitions is, the more thedegree of ordering of the pore array is increased.

The circularity of the micropores seen from the film surface isdramatically improved by dissolving in oxide film dissolution treatment(e) all the anodized film formed by the preceding anodizing treatment(d). Therefore, this cycle is preferably repeated at least twice, morepreferably at least three times and even more preferably at least fourtimes.

In cases where this cycle is repeated at least twice, the conditions ineach cycle of oxide film dissolution treatment and anodizing treatmentmay be the same or different. Alternatively, the treatment may beterminated by anodizing treatment.

(B) Treatment in which Aluminum is Removed from the Oxide Film Obtainedby Treatment (A)

Treatment (B) dissolves and removes the aluminum substrate from theoxide film obtained by the above-described treatment (A). A treatmentsolution which does not readily dissolve the anodized film (alumina) butreadily dissolves aluminum is used for dissolution of the aluminumsubstrate.

That is, use is made of a treatment solution which has an aluminumdissolution rate of at least 1 μm/min, preferably at least 3 μm/min, andmore preferably at least 5 μm/min, and has an anodized film dissolutionrate of 0.1 nm/min or less, preferably 0.05 nm/min or less, and morepreferably 0.01 nm/min or less.

Specifically, a treatment solution which includes at least one metalcompound having a lower ionization tendency than aluminum, and which hasa pH of 4 or less or 8 or more, preferably 3 or less or 9 or more, andmore preferably 2 or less or 10 or more is used for immersion treatment.

Preferred examples of such treatment solutions include solutions whichare composed of, as the base, an aqueous solution of an acid or analkali and which have blended therein a compound of, for example,manganese, zinc, chromium, iron, cadmium, cobalt, nickel, tin, lead,antimony, bismuth, copper, mercury, silver, palladium, platinum or gold(e.g., chloroplatinic acid), or a fluoride or chloride of any of thesemetals.

Of the above, it is preferable for the treatment solution to be based onan aqueous solution of an acid and to have blended therein a chloridecompound.

Treatment solutions of an aqueous solution of hydrochloric acid in whichmercury chloride has been blended (hydrochloric acid/mercury chloride),and treatment solutions of an aqueous solution of hydrochloric acid inwhich copper chloride has been blended (hydrochloric acid/copperchloride) are especially preferred from the standpoint of the treatmentlatitude.

There is no particular limitation on the composition of such treatmentsolutions. Illustrative examples of the treatment solutions include abromine/methanol mixture, a bromine/ethanol mixture, and aqua regia.

Such a treatment solution preferably has an acid or alkali concentrationof 0.01 to 10 mol/L and more preferably 0.05 to 5 mol/L.

In addition, such a treatment solution is used at a treatmenttemperature of preferably −10° C. to 80° C. and more preferably 0 to 60°C.

In the practice of the invention, dissolution of the aluminum substrateis carried out by bringing the aluminum substrate having undergone theabove-described anodizing treatment step into contact with theabove-described treatment solution. Examples of the contacting methodinclude, but are not limited to, immersion and spraying. Of these,immersion is preferred. The period of contact at this time is preferablyfrom 10 seconds to 5 hours, and more preferably from 1 minute to 3hours.

(C) Treatment in which Part of the Micropores Present in the Oxide Filmfrom Which the Aluminum has been Removed by Treatment (B) are Made toExtend Through the Oxide Film

Part of the micropores present in the oxide film from which the aluminumsubstrate has been removed by treatment (B) is subjected to treatment(C) to remove only the bottoms of the part of the micropores in theoxide film to make the part of the micropores present in the oxide filmextend therethrough. This treatment is carried out by bringing only thebottoms of the micropores to be perforated in the oxide film intocontact with an aqueous acid solution or an aqueous alkali solution.Removal of the bottoms of the micropores in the oxide film causes themicropores to extend therethrough.

A specific method that may be preferably used involves forming a patternwhich is insoluble or hardly soluble in an acid or an alkali on asurface of the oxide film after removal of aluminum, and dissolving andremoving the bottoms of portions other than the pattern in the oxidefilm by using the acid or the alkali to make the micropores extendthrough the oxide film.

More specifically, a method that may be preferably used involves forminga photosensitive layer or a thermosensitive layer on a surface of theoxide film after removal of aluminum, forming a pattern by exposure tolight or heat, and dissolving other portions than the pattern of theoxide film by using an acid or an alkali. Use of an alkali is preferredbecause a better pattern is obtained. Preferred examples are shownbelow.

<Formation of Alkali-Developable Thermosensitive Layer/PhotosensitiveLayer>

In the practice of the invention, the alkali-soluble resin contained asthe thermosensitive layer/photosensitive layer are not particularlylimited and any of a monolayer type, a phase-separated type and amultilayer type may be formed.

The alkali soluble resins can be used for the monolayer type recordinglayers such as the photosensitive layers described in JP 7-285275 A andWO 97/39894, phase-separated type recording layers such as thephotosensitive layer described in JP 11-44956 A, and multilayer typerecording layers such as the photosensitive layers described in JP11-218914 A, U.S. Pat. No. 6,352,812B1, U.S. Pat. No. 6,352,811B1, U.S.Pat. No. 6,358,669 B1, U.S. Pat. No. 6,534,238B1 and EP 864420B1, butare not limited thereto.

Illustrative examples of the negative resin composition that may beadvantageously used include negative photosensitive resin compositionsusing diazonium salts as described in paragraphs [0006] to [0019] of JP5-197137 A; photopolymerizable compositions as described in paragraphs[0055] to [0134] of JP 8-320551 A; and photopolymerizable compositionsas described in paragraphs [0007] to [0063] of JP 10-195119 A.

<Perforating Treatment>

The bottom of the oxide film is preferably removed by the method thatinvolves previously immersing the oxide film in a pH buffer solution tofill the micropores with the pH buffer solution from the microporeopening side, and bringing the surface opposite from the openings (i.e.,the bottom of the oxide film) into contact with an aqueous acid solutionor aqueous alkali solution.

When this treatment is to be carried out with an aqueous acid solution,it is preferable to use an aqueous solution of an inorganic acid such assulfuric acid, phosphoric acid, nitric acid or hydrochloric acid, or amixture thereof. The aqueous acid solution preferably has aconcentration of 1 to 10 wt %. The aqueous acid solution preferably hasa temperature of 25 to 40° C.

When this treatment is to be carried out with an aqueous alkalisolution, it is preferable to use an aqueous solution of at least onealkali selected from the group consisting of sodium hydroxide, potassiumhydroxide and lithium hydroxide. The aqueous alkali solution preferablyhas a concentration of 0.1 to 5 wt %. The aqueous alkali solutionpreferably has a temperature of 20 to 35° C.

Specific examples of preferred solutions include a 40° C. aqueoussolution containing 50 g/L of phosphoric acid, a 30° C. aqueous solutioncontaining 0.5 g/L of sodium hydroxide, and a 30° C. aqueous solutioncontaining 0.5 g/L of potassium hydroxide.

The time of immersion in the aqueous acid solution or aqueous alkalisolution is preferably from 8 to 120 minutes, more preferably from 10 to90 minutes and even more preferably from 15 to 60 minutes.

In cases where the film is previously immersed in a pH buffer solution,a buffer solution suitable to the foregoing acids/alkalis is used.

This perforating treatment yields a structure shown in FIG. 3D afterremoval of the aluminum substrate 12 and the barrier layer 18 d, thatis, an insulating base 20 having through micropores 16 d as shown inFIG. 4A. FIG. 4A shows only part of the insulating base where micropores16 d are made to extend through the insulating base by treatment (C).The same holds true for FIGS. 4B to 4D.

(D) Treatment for Filling a Different Material from the Oxide FilmMaterial into the Micropores that were Made to Extend Through byTreatment (C)

In treatment (D), a different material from the oxide film material isfilled into the micropores that were made to extend through by treatment(C), that is, through micropores. In cases where the microstructure ofthe invention is used as an anisotropic conductive member, a metal whichis an electrically conductive material is filled into the throughmicropores. The electrically conductive material to be filled makes upthe conductive paths of an anisotropic conductive member as described inconnection with the microstructure of the invention.

In the inventive manufacturing method, an electrolytic plating processor an electroless plating process may be used for the metal fillingmethod.

In a conventionally known electrolytic plating process that is used forcoloring or other purposes, it is difficult to selectively deposit(grow) metal inside through micropores at a high aspect ratio,presumably because the deposited metal is consumed within the throughmicropores and the plating does not grow even when electrolysis iscarried out for at least a fixed period of time.

Therefore, in the inventive manufacturing method, when metal filling iscarried out by electrolytic plating, it is necessary to provide restperiods during pulse electrolysis or constant potential electrolysis.The rest periods must be at least 10 seconds, and are preferably from 30to 60 seconds.

To promote stirring of the electrolytic solution, it is desirable toapply ultrasound energy.

Moreover, the electrolysis voltage is generally not more than 20 V, andpreferably not more than 10 V, although it is preferable to firstmeasure the deposition potential of the target metal in the electrolyticsolution to be used and carry out constant potential electrolysis atthat potential+not more than 1V. When carrying out constant potentialelectrolysis, it is desirable to use also cyclic voltammetry. To thisend, use may be made of potentiostats such as those available fromSolartron, BAS, Hokuto Denko and Ivium.

Plating may be carried out using a plating solution known in the art.

More specifically, when copper is to be deposited, an aqueous solutionof copper sulfate may generally be used. The concentration of coppersulfate is preferably from 1 to 300 g/L, and more preferably from 100 to200 g/L. Deposition can be promoted by adding hydrochloric acid to theelectrolytic solution. In such a case, the concentration of hydrochloricacid is preferably from 10 to 20 g/L.

When gold is to be deposited, it is desirable to carry out plating byalternating current electrolysis using a sulfuric acid solution of atetrachloroaurate.

According to the electroless plating process, it takes much time tocompletely fill the through micropores having a high aspect ratio with ametal and it is therefore desirable to fill the metal by theelectrolytic plating process in the inventive manufacturing method.

This metal filling treatment yields a microstructure 21 having theconductive paths 5 shown in FIG. 4B as obtained by filling the throughmicropores with a metal.

[Surface Planarization]

In the inventive manufacturing method, the above-described treatment (D)is preferably followed by chemical mechanical polishing to carry outsurface planarization whereby the front side and the back side areplanarized.

By carrying out chemical mechanical polishing (CMP), the front and backsides of the microstructure after the through micropores have beenfilled with other material than the oxide film material can beplanarized while removing excess material adhering to the surfaces afterfilling. Through this treatment, the bottoms of the micropores whichcould not be passed through the oxide film by treatment (C) are removedso that the micropores which were not filled with other material thanthe oxide film material by treatment (D) extend through the oxide film,thereby forming through micropores which are not filled with othermaterial than the oxide film material.

CMP treatment may be carried out by using a CMP slurry such asPNANERLITE-7000 (available from Fujimi Inc.), GPX HSC800 produced byHitachi Chemical Co., Ltd., or CL-1000 produced by AGC Seimi ChemicalCo., Ltd.

It is not preferred to use a slurry for interlayer dielectric films andbarrier metals, because the anodized film should not be polished.

In addition to the CMP treatment, ion milling treatment or electrolyticpolishing treatment may be carried out for surface planarization.

[Trimming]

In cases where the microstructure is used as an anisotropic conductivemember, trimming is preferably carried out after the above-describedtreatment (D) (after the above-described surface planarization in caseswhere this treatment was carried out).

Trimming is a treatment in which only part of the insulating base isremoved from the surface of the microstructure having undergonetreatment (D) (having undergone the above-described surfaceplanarization in cases where this treatment was carried out) to protrudethe metal filled into the through micropores from the insulatingsubstrate surface.

Trimming treatment can be performed under the same treatment conditionsas those of the above-described oxide film dissolution treatment (e)provided a metal making up the conductive paths is not dissolved. It isparticularly preferred to use phosphoric acid with which the dissolutionrate is readily controlled.

This trimming step yields the microstructure 21 as shown in FIG. 4Cwhich has the conductive paths 5 protruded from the insulating substratesurfaces.

In the inventive manufacturing method, the above-described trimming maybe replaced by electrodeposition in which a conductive metal which isthe same as or different from the one filled into the through microporesis further deposited only on the surfaces of the conductive paths 5shown in FIG. 4B (FIG. 4D).

[Protective Film-Forming Treatment]

In the inventive manufacturing method, the micropore size changes withtime by the hydration of the insulating base made of alumina withmoisture in the air and therefore a protective film-forming treatment ispreferably carried out before treatment (D).

Illustrative examples of protective films include inorganic protectivefilms containing elemental zirconium and/or elemental silicon, andorganic protective films containing a water-insoluble polymer.

The method of forming an elemental zirconium-containing protective filmis not subject to any particular limitation, although a commonly usedmethod of treatment involves direct immersion in an aqueous solution inwhich a zirconium compound is dissolved. From the standpoint of thestrength and stability of the protective film, the use of an aqueoussolution in which a phosphorus compound has also been dissolved ispreferred.

Illustrative examples of the zirconium compound that may be used includezirconium, zirconium fluoride, sodium hexafluorozirconate, calciumhexafluorozirconate, zirconium fluoride, zirconium chloride, zirconiumoxychloride, zirconium oxynitrate, zirconium sulfate, zirconiumethoxide, zirconium propoxide, zirconium butoxide, zirconiumacetylacetonate, tetrachlorobis(tetrahydrofuran)zirconium,bis(methylcyclopentadienyl)zirconium dichloride,dicyclopentadienylzirconium dichloride and ethylenebis(indenyl)zirconium(IV) dichloride. Of these, sodium hexafluorozirconate is preferred.

From the standpoint of the uniformity of the protective film thickness,the concentration of the zirconium compound in the aqueous solution ispreferably from 0.01 to 10 wt %, and more preferably from 0.05 to 5 wt%.

Illustrative examples of the phosphorus compound that may be usedinclude phosphoric acid, sodium phosphate, calcium phosphate, sodiumhydrogen phosphate and calcium hydrogen phosphate. Of these, sodiumhydrogen phosphate is preferred.

From the standpoint of the uniformity of the protective film thickness,the concentration of the zirconium compound in the aqueous solution ispreferably from 0.1 to 20 wt %, and more preferably from 0.5 to 10 wt %.

The treatment temperature is preferably from 0 to 120° C., and morepreferably from 20 to 100° C.

The method of forming a protective film containing elemental silicon isnot subject to any particular limitation, although a commonly usedmethod of treatment involves direct immersion in an aqueous solution inwhich an alkali metal silicate is dissolved. The thickness of theprotective film can be adjusted by varying the ratio between thesilicate ingredients silicon dioxide SiO₂ and alkali metal oxide M₂O(generally represented as the molar ratio [SiO₂]/[M₂O]) and theconcentrations thereof in the aqueous solution of an alkali metalsilicate.

It is especially preferable here to use sodium or potassium as M.

The molar ratio [SiO₂]/[M₂O] is preferably from 0.1 to 5.0, and morepreferably from 0.5 to 3.0.

The SiO₂ content is preferably from 0.1 to 20 wt %, and more preferablyfrom 0.5 to 10 wt %.

The organic protective film is preferably obtained by a method whichinvolves direct immersion in an organic solvent in which awater-insoluble polymer is dissolved, followed by heating treatment toevaporate off only the solvent.

Illustrative examples of the water-insoluble polymer includepolyvinylidene chloride, poly(meth)acrylonitrile, polysulfone, polyvinylchloride, polyethylene, polycarbonate, polystyrene, polyamide andcellophane.

Illustrative examples of the organic solvent include ethylenedichloride, cyclohexanone, methyl ethyl ketone, methanol, ethanol,propanol, ethylene glycol monomethyl ether, 1-methoxy-2-propanol,2-methoxyethyl acetate, 1-methoxy-2-propyl acetate, dimethoxyethane,methyl lactate, ethyl lactate, N,N-dimethylacetamide,N,N-dimethylformamide, tetramethylurea, N-methylpyrrolidone,dimethylsulfoxide, sulfolane, γ-butyrolactone and toluene.

The concentration is preferably from 0.1 to 50 wt %, and more preferablyfrom 1 to 30 wt %.

The heating temperature during solvent evaporation is preferably from 30to 300° C., and more preferably from 50 to 200° C.

Following protective film-forming treatment, the anodized film includingthe protective film has a thickness of preferably from 0.1 to 100 μm,and more preferably from 1 to 500 μm.

In the inventive manufacturing method, the hardness and the heat cycleresistance can be controlled by carrying out heating treatment dependingon the application of the microstructure obtained.

For example, the heating temperature is preferably at least 100° C.,more preferably at least 200° C. and even more preferably at least 400°C. The heating time is preferably from 10 seconds to 24 hours, morepreferably from 1 minute to 12 hours and even more preferably from 30minutes to 8 hours. Such heating treatment improves the hardness whilesuppressing the expansion and contraction during the heat cycle ofheating and cooling in the semiconductor manufacturing step.

EXAMPLES Example 1 (A) Mirror-Like Finishing Treatment (ElectrolyticPolishing)

A high-purity aluminum substrate (Sumitomo Light Metal Industries, Ltd.;purity, 99.99 wt %; thickness, 0.4 mm) was cut to a size of 10 cm squarethat allows it to be anodized, then subjected to electrolytic polishingusing an electrolytic polishing solution of the composition indicatedbelow at a voltage of 25 V, a solution temperature of 65° C., and asolution flow velocity of 3.0 m/min.

A carbon electrode was used as the cathode, and a GP0110-30R unit(Takasago, Ltd.) was used as the power supply. In addition, the flowvelocity of the electrolytic solution was measured using the vortex flowmonitor FLM22-10PCW manufactured by As One Corporation.

(Electrolytic Polishing Solution Composition) 85 wt % Phosphoric acid(Wako Pure Chemical 660 mL Industries, Ltd.) Pure water 160 mL Sulfuricacid 150 mL Ethylene glycol  30 mL

(B) Anodizing Treatment (Self-Ordering Method I)

After electrolytic polishing, the aluminum substrate was subjected to 5hours of preliminary anodizing treatment with an electrolytic solutionof 0.30 mol/L sulfuric acid under the following conditions: voltage, 25V; solution temperature, 15° C.; solution flow velocity, 3.0 m/min.

After preliminary anodizing treatment, the aluminum substrate wassubjected to film removal treatment in which it was immersed for 12hours in a mixed aqueous solution (solution temperature, 50° C.) of 0.2mol/L chromic anhydride and 0.6 mol/L phosphoric acid.

Next, the aluminum substrate was subjected to 1 hour of re-anodizingtreatment with an electrolytic solution of 0.30 mol/L sulfuric acidunder the following conditions: voltage, 25 V; solution temperature, 15°C.; solution flow velocity, 3.0 m/min.

Preliminary anodizing treatment and re-anodizing treatment were bothcarried out using a stainless steel electrode as the cathode and using aGP0110-30R unit (Takasago, Ltd.) as the power supply. In addition, usewas made of NeoCool BD36 (Yamato Scientific Co., Ltd.) as the coolingsystem, and Pairstirrer PS-100 (Tokyo Rikakikai Co., Ltd.) as thestirring and warming unit. In addition, the flow velocity of theelectrolytic solution was measured using the vortex flow monitorFLM22-10PCW (As One Corporation).

(C) Aluminum Removal Treatment

Next, the aluminum substrate was dissolved by 3 hours of immersion at20° C. in a 20 wt % aqueous solution of mercuric chloride (corrosivesublimate).

(D) Heating Treatment

Next, the structure obtained as above was then subjected to one hour ofheating treatment at a temperature of 400° C.

(E) Photosensitive Layer-Forming Treatment

Next, the surface of the structure obtained as above from which aluminumhad been removed was coated with a photosensitive layer-forming coatingsolution A of the composition indicated below by a wire bar and driedfor 50 seconds in a drying oven at 140° C. to a coating weight of 0.85g/m².

(Photosensitive Layer-Forming Coating Solution A)

Esterification product of naphthoquinone- 0.45 g 1,2-diazide-5-sulfonylchloride and a pyrogallol-acetone resin (described in Example 1 of U.S.Pat. No. 3,635,709) N-(4-aminosulfonylphenyl)methacrylamide/ 1.10 gmethyl methacrylate (molar ratio: 34:66; weight-average molecularweight: 51,000) 2-(p-methoxyphenyl)-4,6-bis 0.02 g(trichloromethyl)-s-triazine Tetrahydrophthalic anhydride 0.05 gVictoria Pure Blue BOH (available from 0.01 g Hodogaya Chemcial Co.,Ltd.) Megaface F-177 (fluorosurfactant from 0.006 g  Dainippon Ink andChemicals, Inc.) Pluronic F-108 (polyoxyethylene- 0.02 gpolyoxypropylene block copolymer from ADEKA CORPORATION) Methyl ethylketone   10 g 1-Methoxy-2-propanol   10 g

(F) Pattern Image Formation and Removal of Bottom of Oxide Film

In order to form a pattern image on the structure obtained as above, thestructure was then exposed with a 30 A carbon arc light at a distance of70 cm with a transparent positive image in a 10 μm-diameter latticepattern attached in close contact therewith. Then, 0.1 M KOH was used todevelop the microstructure at 25° C. for 20 minutes to remove non-imageareas of the photosensitive layer and further remove the bottom of theanodized film that emerged under the removed layer to thereby prepare astructure having a patterned anodized film having through micropores.The results of the SEM surface images are shown in FIG. 5.

(G) Metal Filling Treatment

Next, gold was vapor-deposited on the side of the structure having thepattern formed thereon after heating treatment to attach a goldelectrode in close contact therewith, and electrolytic plating wascarried out using the gold electrode as the cathode and copper as theanode.

A mixed solution of copper sulfate=200/50/15 (g/L) held at 25° C. wasused as the electrolytic solution to carry out constant-voltage pulseelectrolysis, thereby manufacturing a microstructure having the throughmicropores filled with copper.

An electroplating system manufactured by Yamamoto-MS Co., Ltd. and apower supply (HZ-3000) manufactured by Hokuto Denko Corp. were used tocarry out constant-voltage pulse electrolysis. The deposition potentialwas checked by carrying out cyclic voltammetry in the plating solution,following which the film side potential was set to −2 V and electrolysiswas carried out. The pulse waveform in constant-voltage pulseelectrolysis was a square waveform. Specifically, electrolysistreatments lasting 60 seconds at a time were carried out a total of fivetimes with 40-second rest periods between the respective treatments, soas to provide a total electrolysis treatment time of 300 seconds.

The surface of the anodized film after filling with copper was observedby FE-SEM and as a result the copper was found to partially protrudetherefrom.

(H) Surface Planarizing Treatment

Next, CMP treatment was carried out on the front and back sides of thecopper-filled structure.

PLANERLITE-7000 (available from Fujimi Inc.) was used as the CMP slurry.

(I) Trimming Treatment

The CMP-treated structure was then immersed in a phosphoric acidsolution so as to selectively dissolve the anodized film, therebycausing the copper columns serving as the conductive paths to protrudefrom the surface.

The same phosphoric acid solution as in the above-described perforatingtreatment was used, and the treatment time was set to 5 minutes.

Then, the structure was rinsed with water, dried and observed by EF-SEM.

As a result, it was confirmed that copper was only filled into the poreswithin the 10 μm-diameter areas, the protruded portions of theconductive paths had a height (bump height) of 10 nm, the conductivepath diameter which is the size of the electrode portion was 40 nm andthe member had a thickness of 50 μm.

Example 2

The respective treatments (A) to (H) were carried out as in Example 1and a treatment for covering the copper protruded from the surfaces ofthe insulating base (anodized film) with gold.

More specifically, the microstructure obtained after trimming treatmentin Example 1 was plated by immersion at 70° C. for 10 seconds in a goldelectroless plating solution (Melplate AU-601 from Meltex Inc.).

The microstructure was observed by EF-SEM as in Example 1 and theprotruded portions were found to be rounded and to have an increasedbump height of about 20 nm. It was also confirmed that the conductivepath diameter which is the size of the electrode portion was 40 nm andthe member had a thickness of 50 μm.

Example 3

Example 1 was repeated under the same conditions except that preliminaryanodizing treatment and re-anodizing treatment in the anodizingtreatment step B (self-ordering method I) were carried out by using anelectrolytic solution of 0.50 mol/L oxalic acid under the followingconditions: voltage, 40V; solution temperature, 15° C.; solution flowvelocity, 3.0 m/min, and trimming treatment (G) was carried out for 10minutes, thereby manufacturing a microstructure.

The microstructure was observed by EF-SEM as in Example 1 and it wasconfirmed that the bump height was 40 nm, the conductive path diameterwhich is the size of the electrode portion was 120 nm and the member hada thickness of 50 μm.

1-15. (canceled)
 16. A method of manufacturing a microstructurecomprising a base having through micropores at a density of at least 10⁷micropores/mm², part of the through micropores being filled with othermaterial than a material of the base, wherein an aluminum substrate issubjected at least to, in order, a treatment (A) for anodizing thealuminum substrate to form an oxide film having micropores; a treatment(B) for removing aluminum from the oxide film obtained by the treatment(A); a treatment (C) for perforating part of the micropores present inthe oxide film from which the aluminum was removed by the treatment (B);a treatment (D) for filling the part of the micropores that wereperforated by the treatment (C) with a different material from an oxidefilm material; and a step (E) of surface planarization for removingbottoms of micropores of the oxide film that were not perforated in thetreatment (C) to make the unperforated micropores extend through theoxide film.
 17. The microstructure manufacturing method according toclaim 16, wherein, in order to perforate the part of the microporespresent in the oxide film in the treatment (C), the treatment (C)comprises at least a treatment (C′) which comprises: forming a patternwhich is insoluble or hardly soluble in an acid or an alkali on asurface of the oxide film after removal of the aluminum; and dissolvingportions other than the pattern in the oxide film by using the acid orthe alkali to make the micropores formed in the portions other than thepattern in the oxide film extend through the oxide film.
 18. Themicrostructure manufacturing method according to claim 17, wherein thetreatment (C′) comprises at least a treatment (C′-1) which comprises:forming a photosensitive layer in which solubility with respect to theacid or the alkali changes in response to light on the surface of theoxide film after the removal of the aluminum; irradiating thephotosensitive layer with light beams; and dissolving the photosensitivelayer by using the acid or the alkali to form the pattern which isinsoluble or hardly soluble in the acid or the alkali on the surface ofthe oxide film after the removal of the aluminum.
 19. The microstructuremanufacturing method according to claim 17, wherein the treatment (C′)comprises at least a treatment (C′-2) which comprises: forming athermosensitive layer in which solubility with respect to the acid orthe alkali changes in response to heat on the surface of the oxide filmafter the removal of the aluminum; heating the thermosensitive layer;and dissolving the thermosensitive layer by using the acid or the alkalito form the pattern which is insoluble or hardly soluble in the acid orthe alkali on the surface of the oxide film after the removal of thealuminum.
 20. The microstructure manufacturing method according to 16,wherein, in the treatment (D), the different material from the oxidefilm material filled into the micropores that were made to extendthrough the oxide film by the treatment (C) is an electricallyconductive material.
 21. The microstructure manufacturing methodaccording to 17, wherein, in the treatment (D), the different materialfrom the oxide film material filled into the micropores that were madeto extend through the oxide film by the treatment (C) is an electricallyconductive material.
 22. The microstructure manufacturing methodaccording to 18, wherein, in the treatment (D), the different materialfrom the oxide film material filled into the micropores that were madeto extend through the oxide film by the treatment (C) is an electricallyconductive material.
 23. The microstructure manufacturing methodaccording to 19, wherein, in the treatment (D), the different materialfrom the oxide film material filled into the micropores that were madeto extend through the oxide film by the treatment (C) is an electricallyconductive material.
 24. The microstructure manufacturing methodaccording to claim 20, wherein, in the treatment (D), the microporesthat were made to extend through the oxide film by the treatment (C) arefilled with the electrically conductive material by electrolyticplating.
 25. The microstructure manufacturing method according to claim21, wherein, in the treatment (D), the micropores that were made toextend through the oxide film by the treatment (C) are filled with theelectrically conductive material by electrolytic plating.
 26. Themicrostructure manufacturing method according to claim 22, wherein, inthe treatment (D), the micropores that were made to extend through theoxide film by the treatment (C) are filled with the electricallyconductive material by electrolytic plating.
 27. The microstructuremanufacturing method according to claim 23, wherein, in the treatment(D), the micropores that were made to extend through the oxide film bythe treatment (C) are filled with the electrically conductive materialby electrolytic plating.